The Joker is one of Batman's main enemies. The Joker's origins are shrouded in mystery but it is believed he dived into vat of chemicals to escape Batman. With his skin bleached and lips permanently formed into smile, he went insane and became the Clown Prince of Crime. In Robin's version of the Teen Titans' origin story, he claimed to have left Gotham City without quarrel after he helped Batman capture the Joker. Joker was seen in Jump City when Robin and Cyborg sang their Real Boy Adventure song. He was later duped into giving $100 to Cyborg, Raven, and Starfire in a pyramid scheme. Joker and Penguin were invited to Batman and Commissioner Gordon's slumber party without Alfred Pennyworth's knowledge. Some time into the night, Joker sent a text to Batman and he let them in from the Batcave's window. The Penguin fell and made a noise. They quickly hid in Batman and Gordon's sleeping bags and were undetected by Pennyworth. They later played the shaving cream prank on Gordon and laughed at his impression of Two-Face. Pennyworth caught them red-handed. Joker and Penguin met up with them on the roof of police headquarters with a giant umbrella and coffee after it started raining.

An opulent fireworks display set off by Cyborg caught the attention of Catwoman, Penguin, Joker, Poison Ivy, and Riddler. They raided the manor and looted everything. The Titans were no match for them. Robin sprang ahead of Joker and attacked with his staff. Joker parried with his bag and dodged then sprayed gas from his lapel flower onto Robin's face. Alfred Pennyworth returned to the manor and made short work of the villains. He tickled Joker with a brush then smacked his head with it.